The long term objective is to develop our new immunoassay method for use in the dentist's and physician's office. Our method will use the evanescent wave on the surface of an optical fiber to optically separate bound from unbound antigen/antibody and to minimize the fluorescent background of the specimen. The fiber is in raw specimen contained in a capillary tube which minimizes specimen handling and sensitivity to specimen volume. It also corrects for interstitial volume. It will use only a few microliters of unprocessed specimen (e.g., raw saliva or whole blood). The fluorescent tagged reagents will have a long shelf life. The instrument may be about the size of a pocket calculator. The variety of assays possible will include hormones, drugs and infectious agents. We expect that our method will make immunoassay practical for use in the dentist's and doctor's office. It will have an impact on the method of delivery of health care since there will be no need to wait for "results from the lab" but rather the results will be available during the visit. The specific aim is to determine the accuracy of the interstitial volume correction in raw saliva.